INTRODUCTION INTRODUCTION
Engineered brick masonry design is a rational design procedure based on material properties and fundamental engineering analysis principles. This type of approach, as opposed to an empirical approach, permits the designer to retain the aesthetic qualities of brick masonry and make efficient use of brick masonry's structural properties.
Since engineered brick masonry design is dependent on material properties, minimum material strength require-ments are determined in the preliminary design phase. Materials (brick, mortar and grout) are selected and may be tested to determine allowable design stresses for the combination of materials selected (see Technical Notes 39A). Quality assurance testing is then performed during construction to evaluate the properties of constructed masonry. The results of these tests are then used to determine if the constructed masonry is acceptable.
This Technical Notes discusses standards developed by the American Society for Testing and Materials (ASTM) that may be used for quality assurance testing of engi-neered brick masonry. This Technical Notes is not intend-ed to replace applicable ASTM standards, but to supple-ment them.
The purpose of this Technical Notes is to serve as an aid in selecting, applying and interpreting tests. The engi-neer, architect or other responsible person must use judg-ment in selecting and applying these test methods, but it is hoped that this Technical Notes will aid in that process. PURPOS
PURPOSE OF QUALITYE OF QUALITY ASSURANASSURANCE TESTINGCE TESTING Several standards are used in the United States for the design of brick masonry structures. These standards are referenced in most building codes and contain some type of requirement for testing of materials and
assem-blages to evaluate material properties, design parameters or as a means of quality assurance. Quality assurance testing is specifically performed to determine that the materials, construction and workmanship meet the project specifications.
The BIA Standard (Building Code Requirements for Engineered Brick Masonry , Brick Institute of America, McLean, Virginia, August 1969), for example, requires inspection and testing in order for the designer to make use of higher allowable design stresses. Allowable stress values under the BIA Standard are divided into two cate-gories: "With Inspection" and "Without Inspection". If no inspection is provided, the design allowables for "Without Inspection" are used and represent a thirty-three percent reduction in magnitude, as compared to the values per-mitted for "With Inspection". Therefore, it is advantageous to implement quality assurance measures in some cases to permit higher allowable stress values.
The type of inspection required in the BIA Standard typically consists of an inspector (the engineer, architect or other responsible party) and some type of testing. The tests outlined in this Technical Notes are those that are most commonly performed to satisfy the requirements of the BIA Standard.
TESTING METHODS TESTING METHODS
The ASTM standards commonly used for quality assurance testing of brick masonry materials and assem-blies are contained in the Annual Book of ASTM
Standards. Current copies of applicable standards should be readily available to laboratory personnel, individuals involved in field sampling and testing, and individuals involved in interpreting test results. The applicable ASTM standards are: March 1988
39B
39B
REVISED
REVISED
T
Technic
echnical No
al Notes
tes
on Brick Construction
on Brick Construction
Brick Industry Association
Brick Industry Association 11490 Commerce Park Drive, Reston, Virginia 20191
TESTING FOR ENGINEERED
TESTING FOR ENGINEERED BRICK MASONRY
BRICK MASONRY
QUAL
QUALITY
ITY ASSU
ASSURANCE
RANCE
Abstract:
Abstract: Testing prior to and during the construction of engineered brick masonry may be required to provide a means of quality assurance. Testing may cover materials, to determine compliance with the project require-ments; assemblies, to determine the properties of the masonry as constructed or to establish the properties of masonry in existing structures. The extent of testing required must be determined by the engineering or archi-tectural firm responsible for the project design and will depend upon the complexity and importance of the ject. This Technical Notes describes quality assurance procedures applicable to brick masonry assemblies;
other issues in this series address testing of component materials and testing to establish allowable design stresses.
Key Words:
Key Words: brickbrick, bond strengthbond strength, diagonal tensiondiagonal tension, engineered brick masonry, grout, masonry testing, mortar, prism testing prism testing, quality assurancequality assurance, shear, testingtesting.
Component Materials Component Materials Clay Masonry Units
ASTM C 67, Standard Method of Sampling and Testing Brick and Structural Clay Tile.
Mortar
ASTM C 270, Standard Specification for Mortar for Unit Masonry.
ASTM C 109, Standard Test Method for Compressive Strength of Hydraulic Cement Mortars (using 2-in. or 50-mm Cube Specimens). ASTM C 780, Standard Method for
Preconstruction and Construction Evaluation of Mortars for Plain and Reinforced Unit Masonry. Grout
ASTM C 476, Standard Specification for Grout for Masonry.
ASTM C 1019, Standard Method for Sampling and Testing Grout.
Assemblies Assemblies
Masonry Compressive Strength
ASTM E 447, Standard Test Methods for Compressive Strength of Masonry Prisms. Flexural Bond Strength
ASTM E 518, Standard Test Methods for Flexural Bond Strength of Masonry.
ASTM C 1072, Standard Method for Measurement of Flexural Bond Strength. In addition to the preceding standards, other stan-dards, while not generally used for quality assurance test-ing, may be performed in conjunction with compressive and/or flexural bond strength tests to establish a relation-ship between test methods for quality assurance purpos-es. These methods listed below are discussed in detail in Technical Notes 39A.
Flexural Tensile Strength
ASTM E 72, Standard Method of Conducting Strength Tests of Panels for Building Construction.
Shear Strength Diagonal Tension (Shear)
ASTM E 519, Standard Test Method for Diagonal Tension (Shear) in Masonry Assemblages. Typically, ASTM standards provide clear and concise explanations of the procedures involved in sampling and testing; however, for the novice, some areas may be con-fusing. Technical Notes 39 Revised presents a complete discussion of the preceding standards for testing compo-nent materials. The standards are listed here for the sake of completeness only. The remaining standards relating to the testing of masonry assemblages are the subject of this Technical Notes.
LABORA
LABORATORTORYY SELECTISELECTIONON
A laboratory selected to perform mas onry testing should be properly staffed and be experienced in masonry testing. The equipment available at a laboratory will directly affect the types of tests that can be performed, and the specimens that can be tested. As a minimum, a laboratory will require a curing room with controlled tem-perature and humidity, and a compression testing
machine with a minimum capacity of 300,000 lb and a 15-in. stroke to perform prism tests. Other test methods described in this Technical Notes require more specialized equipment that may not be available at some laboratories. EVALUATION O
EVALUATION OF F MASONRMASONRYY STRENGTHSTRENGTH Compressive Strength
Compressive Strength General.
General. Masonry assembly compressive strength should be determined by prism tests in accordance with ASTM E 447, Method B (see Figure 1).
Specimens.
Specimens. A minimum of three prisms should be constructed, using the same materials and workmanship as used in the project. The mortar bedding, joint thick-ness, joint tooling, bonding arrangement and grouting pat-tern should be the same as that in the project. No
struc-Prism Test Schematic Prism Test Schematic
FIG. 1 FIG. 1 2
tural reinforcement should be included; however, metal wall ties may be included if used in the project. Prisms should not be grouted unless all hollow cells and spaces in the actual construction are to be grouted.
The prism thickness should be the same as that of the actual construction. The prism length should be equal to or greater than the prism thickness. The height of the prism should be at least twice the prism thickness or a minimum of 15 in. (375 mm).
Handling and Curing.
Handling and Curing. Prisms should be constructed on the jobsite in an area where they will not be disturbed or damaged. Prisms should be subjected to atmospheric conditions similar to those of the masonry they represent for a period of 48 hr prior to being prepared for transporta-tion to the testing laboratory. Prisms should be secured and transported in such a manner so as not to damage them.
After prisms are delivered to the laboratory, they should be cured in laboratory air, free of drafts, at 75 deg F ±15 deg F (24 deg C ± 8 deg C), with a relative humidi-ty between 30 and 70% for a period of 26 additional days.
Capping.
Capping. Proper capping of prisms cannot be over-emphasized. Brick units are not perfectly formed and their bearing surfaces may not be parallel and free from surface irregularities. The purpose of capping the bearing surfaces is to assure reasonably parallel and smooth bearing planes. This reduces the likelihood of uneven bearing and stress concentrations that can result in pre-mature prism failure. The capping material itself should have a compressive strength in excess of that expected of the prism to insure that the capping material does not fail before the prism.
Laboratory personnel responsible for capping prisms should be knowledgeable of the capping procedures pre-scribed in ASTM C 67 and C 140. Poor capping tech-niques and inappropriate capping materials can result in erratic test results and lower apparent prism compressive strengths.
Testing.
Testing. Prisms should be centered under the spher-ical upper bearing block of the testing machine so that the resulting load will be applied through the center of gravity of each specimen. This is extremely important since the introduction of an eccentric load, if the specimen is not properly centered, can result in lower apparent prism compressive strength.
The speed of testing specified in ASTM E 447 should be followed to obtain consistent results. Past experience on the effect of the loading rate on compressive strength has shown that, as the loading rate increases, there may be a significant increase in apparent compressive strength. The prescribed loading rate provides a moder-ate rmoder-ate of loading that produces more consistent results and more accurately represents the true prism compres-sive strength.
Calculation and Report.
Calculation and Report. The ultimate compressive strength of a prism is calculated by dividing the maximum compressive load by the cross-sectional area of the prism. For prisms constructed with solid units (ASTM C 216 or ASTM C 62), or units grouted solid, the gross cross-sectional area is used to calculate compressive
strength. For prisms constructed with ungrouted hollow units (ASTM C 652), the net cross-sectional area (deter-mined by the procedure described in ASTM C 67) is used in the calculation. When brick masonry prisms with height-to-thickness ratios (h/t) of less than 5 are tested, the ultimate compressive strength, as calculated above, must be multiplied by the factors given in Table 1 to cor-rect for slenderness effects.
The report should contain the prism dimensions, prism age, description of materials, maximum compres-sive load for each prism, cross-sectional area of each prism, compressive strength of each prism, average com-pressive strength of the specimens, standard deviation and coefficient of variation.
Recommendations and Evaluation.
Recommendations and Evaluation. When prism tests are used as a means of quality assurance for the BIA Standard, not less than 3 prisms should be construct-ed for each 5000 sq ft of wall area or each story height, whichever is more frequent. Additional test prisms may be constructed at the discretion of the engineer or archi-tect.
Often it is desirable to establish strength relationships for prisms cured less than 28 days to prisms cured for 28 days. This may be established by testing one set of 3 prisms (5 prisms preferred), constructed for each curing period. The prisms should be cured at the site for 24 hr and transported to the laboratory and stored with an ambi-ent temperature and humidity as prescribed in ASTM E 447 for the remainder of the curing period. One set of prisms should be tested at 28 days and the other set test-ed at the desirtest-ed age level, typically, 3 or 7 days. From this data, strength relationships between shorter curing periods and 28-day curing periods may be developed.
It is desirable to establish the relationship between early prism strengths to 28-day strengths by testing. However, if this relationship is not or cannot be estab-lished, an approximate method may be used to predict the 28-day prism compressive strengths.
The work represented by the quality assurance speci-mens may be deemed acceptable if the average 28-day compressive strengths or the projected average 28-day compressive strengths are not less than the specified design compressive strength.
TABLE 1 TABLE 1aa Slenderness Ratiob 2.0 2.5 3.0 3.5 4.0 4.5 5.0 Correction Factorc 0.82 0.85 0.88 0.91 0.94 0.97 1.00 a
These values are different from those now given in the August 1969 BIABuilding Code Requirements for Engineere d Brick Masonry. They are based on subsequent research and more nearly reflect the masonry behavior in prisms with h/t less than 5.
b
Height to thickness (h/t).
c
Interpolate to obtain intermediate values.
Diagonal Tension (Shear) Strength Diagonal Tension (Shear) Strength
General.
General. Under certain circumstance, it is sometimes necessary to directly establish design shear stresses more accurately than values established as a function of compressive strength (see allowable shear stresses in the BIA Standard). When this is the case, the methods out-lined in ASTM E 519 or ASTM E 72 are used to establish design values (see Technical Notes 39A). These test methods require large masonry specimens and cannot be used practically as quality assurance tests. However, these tests may be performed with companion compres-sive test specimens to develop a relationship between shear and compressive test results. This permits testing of smaller compressive specimens as a means of quality assurance.
Companion Specimens.
Companion Specimens. Compressive test prisms should be constructed and tested as outlined in Technical Notes 39A. A minimum of 3 prisms (preferably 5 prisms) should be constructed and tested. The data collected from the compressive prism tests and diagonal tension tests can be used to establish a relationship between prism compressive strength and design shear strength. When this relationship is established, tests can then be conducted by ASTM E 447, in lieu of ASTM E 72 and E 519.
FLEXURA
FLEXURALL BOND BOND STRENGSTRENGTHTH General.
General. ASTM E 518 or C 1072 may be used as quality assurance tests to measure the flexural bond strength between masonry units and mortar. These tests are not intended for use in establishing design stresses. Design stresses should be established through ASTM E 72, as described in Technical Notes 39A.
Companion Specimens.
Companion Specimens. A relationship between the flexural bond strength obtained by ASTM E 518 or ASTM C 1072 and the transverse strength of ASTM E 72 may be developed by testing companion specimens. This requires that ASTM E 72 transverse load tests be per-formed and that companion specimens, as prescribed in ASTM E 518 or ASTM C 1072 be constructed and tested using the same units, mortar and workmanship as the E 72 tests. The data from these tests can then be used to establish the relationship between the transverse flexural strength and the flexural bond strength.
Once this relationship has been established, ASTM E 72 tests need not be conducted. Quality assurance tests can then be made by ASTM E 518 or ASTM C 1072.
ASTM E 518 Test.
ASTM E 518 Test. E 518 provides two methods for performing tests on flexural beams. Method A uses con-centrated loads at 1/3 points of the span (see Fig. 2). Method B uses a uniform loading over the entire span (see Fig. 3) applied by an air bag.
Specimens ---- Prisms should be built at the jobsite with the same materials and workmanship as the actual construction.
Prisms constructed in the field for quality assurance testing should be protected from damage, but exposed to the same atmospheric conditions as the constructed
masonry. These prisms should be stored at the jobsite until the testing date.
Testing -- While ASTM E 518 does not specify the orientation of the specimens, specimens for both Method A and Method B (see Figs. 4 and 5) should be placed with the tooled joints downward; that is, loads should be applied to the unfinished face. This provides a more stan-dardized test and allows a more accurate comparison of results.
If Method A is used and failure of any specim en occurs outside of the middle third of the specimen, the test results for that specimen should be discarded.
Calculation and Report -- After testing is completed, the gross area modulus of rupture (tensile bond strength) can be calculated using one of the following formulae:
Method A test ; specimen made of solid masonry units. R = (P + 0.75 PS)
bd2 (Eq. 1)
E518 Met
E518 Method Ahod A TTestest FIG. 2 FIG. 2
E518 Method B Test E518 Method B Test
FIG. 3 FIG. 3
where:
R = gross area modulus of rupture, psi (Mpa) P = maximum machine-applied load, lb (N) Ps= weight of specimen, lb (N)
= span, in. (mm)
b = average width of specimen, in. (mm) d = average depth of specimen, in. (mm)
Method B test; specimen made of solid masonry units. R = 0.75 (P + PS) (Eq. 2)
bd2
Method A test ; specimen made of hollow masonry units. R = (0.167 P + 0.125 PS) (Eq. 3)
S where:
S = section modulus of actual net bedded area, in.3 (mm3)
Method B test; specimen made of hollow masonry units. R = 0.125 ( P + PS) (Eq. 4)
S
For calculation of the section modulus based on the net bedded areas of hollow units, the following formulae may be used:
Fully bedded hollow units; (see Fig. 6). S = bd3-(b1d1 3 + b2d2 3 + b3d3 3 ...bndn 3 ) 6d (Eq. 5) where:
b1= width of cores, in. (mm)
d1= depth of cores, in. (mm)
Face shell bedded hollow units; (see Fig. 7). S = b (d3-d1
3
) (Eq. 6)
6d ASTM C 1072 Test.
ASTM C 1072 Test. ASTM C 1072, commonly known as the "bond wrench test", permits individual mortar joints to be tested for flexural bond strength by applying an eccentric load to a single joint in a prism (see Fig. 8). This method has several advantages over the ASTM E 518 test method in that: 1) More data is collected from each prism. 2) The data gathered is more representative since each joint in a specimen is tested instead of the weakest joint in the specimen. 3) It may be used to test specimens extracted from existing structures. 4) Joints remaining after testing by the ASTM E 518 method may be tested and the results of the two methods compared.
Specimens -- Prisms should be constructed at the jobsite with the same materials and workmanship used in
the actual construction. Prisms should be constructed in a
E518
E518 Method Method AA SetupSetup FIG. 4 FIG. 4
E518 Method B Setup E518 Method B Setup
FIG. 5 FIG. 5
Cross Section
Cross Section -- Full Bedded -- Full Bedded Hollow Hollow UnitUnit FIG. 6
FIG. 6 5
location where they will not be disturbed or damaged, but be subjected to atmospheric conditions similar to those of the actual masonry.
Prisms should be a minimum of 2 units in height, with a minimum width of 4 in. (200 mm). It is recommended that the prisms be a full unit in width. Joints should be 3/8 in. ± 1/16 in. (9.4 mm ± 1.6 mm) in thickness. One face of each prism should be tooled to match the tooling of the project. Prisms should be stored at the jobsite until the testing date. As a minimum, 5 joints should be tested.
Testing -- Prisms should be placed in the support frame so that the tooled joints face the clamping bolts in the loading arm and are subjected to flexural tension (see Fig. 8). Prisms should be positioned vertically such that a single brick projects above the lower clamping bracket. A soft bearing material a minimum of 1/2 in. (13 mm) in thickness should be placed between the bottom of the prism and the adjustable prism support base. The loading arm clamping bolts should be tightened using a torque of
Cross Section -- Face Shell Bedded Hollow Unit Cross Section -- Face Shell Bedded Hollow Unit
FIG. 7 FIG. 7
Bond Wrench Test Apparatus Bond Wrench Test Apparatus
FIG. 8 FIG. 8 6
not more than 20 lb-in. (2.3 N-m). Loading should be applied at a uniform rate such that the total load is applied in not less than 1 min. nor more than 3 min.
Calculation and Repo rt -- After testing is completed, the flexural bond strength can be calculated as:
Specimens made of solid masonry units
Fg = 6 (PL + P1L1) - (P + P1) (Eq. 7)
bd2 bd
where:
Fg = gross area flexural tensile strength, psi (MPa),
P = maximum machine-applied load, lb (N),
P1= weight of loading arm, lb (N) (See Appendix XI in
ASTM C 1072)
L = distance from cent er of prism to loading point , in. (mm),
L1= distance from center of prism to centroid of load
ing arm, in. (mm) (See Appendix XI in ASTM C 1072)
b = average width of the cross-section of failure sur face, in. (mm),
d = average thickness of cross-section of failure sur face, in. (mm)
Specimens made of hollow masonry units Fn = (PL + P1L1) - (P + P1) (Eq. 8)
S A
where:
Fn = net area flexural tensile strength, psi (MPa), S = section modulus of actual net bedded area, in.3
(mm3),
A = net bedded area, in.2(mm2).
For calculation of section modulus, see Eqs. 5 and 6 and Figs. 6 and 7. The net bedded area may be calculat-ed as:
Fully bedded hollow units; (see Fig. 6)
A = bd - (b1d1- b2d2+ b3d3...bndn) (Eq. 9)
Face shell bedded hollow units; (see Fig. 7)
A = b (d -d1) (Eq. 10)
EVALUATION OF TEST RESULTS EVALUATION OF TEST RESULTS General
General
In most cases, strength levels are established by test-ing or by the selection of design values. Evaluation then becomes a simple matter of comparing the results of the quality assurance tests with the desired strength levels.
Unsatisfactory Test Results Unsatisfactory Test Results
Examination of Procedures.
Examination of Procedures. Several alternatives are available when test results fall below the required level. If backup specimens are not available for testing, then close examination should be made of the method of prism construction, the handling of the specimens during transportation and storage and of the laboratory facilities and test procedures. Actual stresses should be checked to determine if the lower strength will provide structural stability. After the above observations and calculations are completed, some judgments should then be made. They are:
1. Did mortar proportions or properties change? 2. Did brick properties change?
3. Were there unusual curing conditions? 4.Were specimens damaged during transit or stor
age?
5. Were specimens properly constructed? 6. Were test procedures properly followed? 7. Were calculations correctly performed?
As a result of these questions, the possible cause of low test results may be determined.
Alternate Test Procedure.
Alternate Test Procedure. If no immediate solution is evident and reduced strengths result in safety factors below an acceptable level, prisms may be cut from the area in question and tested as described previously.
After specimens are cut from the wall, they should be transported to the lab for testing. If specimens are cut by a water-cooled saw, they should be allowed to dry prior to testing.
Exercise of Judgment.
Exercise of Judgment. If the test results are still low, then a judgment is required. If the field-cut specimen tests result in strengths that lower the factor of safety below an acceptable level, then removal of the masonry in question must be considered. Obviously, this is the last resort after all other possibilities have been closely exam-ined.
SUMMARY SUMMARY
This Technical Notes has discussed quality assurance testing based on procedures developed by ASTM. Testing agencies using these ASTM test methods should be fully aware of their procedures and limitations, so that improper application and erroneous results are avoided.
While the testing procedures outlined in this Technical Notes are primarily for engineered brick masonry under the BIA Standard, they may also be used for non-structur-al masonry testing and qunon-structur-ality assurance testing under other standards. Excessive testing can add unnecessary cost to the project. It is important that care be exercised to avoid excessive testing.
It should also be pointed out that, while strengths are important properties of masonry, they are not the only desirable properties. Strengths should not become so important that other desirable properties of masonry are sacrificed. It is still important that masonry be resistant to water penetration, provide sound control and be properly detailed. Quality assurance testing is just one tool to
vide assurance that all of the desirable properties of brick masonry are obtained.
Testing procedures described in this Technical Notes may involve the use of hazardous materials, operations and/or equipment. This Technical Notes does not purport to address all of the safety practices associated with the use of these test methods. It is the responsibility of the user of this Technical Notes to establish appropriate safe-ty and health practices and determine the applicabilisafe-ty or regulatory limits prior to the use of the test methods described.
The information contained in this Technical Notes is based on the available data and experience of the techni-cal staff of the Brick Institute of America. The information should be recognized as recommendations which, if fol-lowed with judgment, should prove beneficial to the per-formance of masonry construction.
Final decisions on the use of information, details and materials as discussed in this Technical Notes are not within the purview of the Brick Institute of America and must rest with the product designer, owner or both.
